Lyme disease is virtually a household name today, but there was a time when it was not. What is Lyme disease?
In 1975, in the town of Lyme, Connecticut, a new disease began to be recognized after clusters of children were diagnosed with arthritis. The connection between this puzzling disease and the bite of a deer tick was discovered 6 years later, in 1981, yet Lyme disease infections continue to represent the most common insect-borne disease in the United States. It is relatively easy to treat when caught early, but it can have chronic life-altering complications when untreated.
Species Name: Borrelia burgdorferi
Type of Microbe: Spirochete bacteria
How it Causes Disease: Borrelia burgdorferi bacteria enters the tissue at the site of a tick bite, multiplies locally and migrates to the skin, where it causes a characteristic bulls-eye rash. It then migrates throughout the body to multiple organs, including the brain, heart and muscles. The body’s immune system reacts with an inflammatory response against the bacteria.
How it Spreads: Lyme disease is spread through bites of infected Ixodes ticks that carry the bacteria. These ticks include deer ticks, western black-legged ticks, and black-legged ticks, which are much smaller than common dog or cattle ticks. Transmission does not occur from person-to-person or from animal-to-person.
Who’s at Risk? All people can get the disease, but people who spend more time outdoors are at greater risk. Most cases are reported in the summer months. Ticks that spread Lyme disease are found in temperate forested areas of Europe, Asia, and North America (north east, north central, and Pacific coast). Spread of Lyme disease does not occur in tropical climates. In the United States, most cases occur in people ages 5 to 14 and 45 to 54 years of age.
Symptoms of Lyme Disease: The characteristic early symptom of Lyme disease is a skin rash called “erythema migrans,” where the tick bite occurred. The rash appears as a bulls-eye, with red edges surrounding a clear center. The rash occurs a few days to a month following the bite, although approximately one-fifth of infected people do not report a rash. The rash resolves spontaneously in 3 to 4 weeks. In addition to the rash, early symptoms of Lyme disease are similar to getting the flu, such as extreme fatigue, fever, headache, and muscle aches.
The second stage of disease can last days to months. During this stage, the infection reaches the neural tissue, where it can cause inflammation of the brain (meningitis, encephalitis). Spread of infection to the heart can also result in inflammation in the heart.
The third and final stage of the disease is characterized by chronic arthritis and chronic neurological disorder. This stage can last for months to years.
Diagnosis: Diagnosis of Lyme disease includes confirmation of a history of exposure to potentially infected ticks and physical findings, such as the characteristic rash. A characteristic rash that occurs in an at-risk geographic area is enough to prompt treatment. In less clear cases, blood tests are necessary to make the diagnosis; tests seek to detect the type of antibodies made in response to Borrelia burgdorferi. However, it is important to note that the immune system takes 2 to 5 weeks to develop a response, so a person may not test positive for the antibodies until that time. As such, antibodies are often not useful in the setting of a very recent exposure.
Prognosis: With early treatment, the prognosis is generally good. Without treatment, there are several potential complications (see below).
Treatment: Early treatment with antibiotics is usually effective in shortening the duration of the disease. Commonly prescribed antibiotics for early disease include oral forms of doxycycline, amoxicillin, or cefuroxime axetil. Late treatment may require more than one antibiotic treatment, often given intravenously. A small percentage of patients do not recover from Lyme disease following antibiotic therapy; they may require use of anti-inflammatory drugs or surgery for relief of symptoms.
Complications: There are many potential complications of Lyme disease, particularly when left untreated. These complications include Bell's palsy, inflammation of the eye (ophthalmitis), cognitive disorders including memory loss, and congestive heart failure.
Prevention: Following outcries of concern regarding variability in safety and effectiveness, the Lyme disease vaccine, LYMErix, manufactured by GlaxoSmith Kline, was taken off the market in 2002. New vaccines are currently being developed.
To avoid bites from infected ticks, take the following special precautions when hiking or camping in areas where ticks are found, such as wooded, brushy and grassy areas:
- Wear long pants and long-sleeved shirts.
- Wear shoes that provide adequate coverage.
- Use DEET-containing insect repellent.
- Avoid high-risk areas, such as wooded, brushy, and grassy areas, especially in late spring and early summer.
- Carefully check your body for ticks following outdoor activities.
Sources
Center for Disease Control. MMWR Weekly Report. Lyme Disease – United States, 2003-2005.
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5623a1.htm
U.S. Departments of Health and Human Services. National Institutes of Health. Lyme Disease. The Facts The Challenge. Accessed March 10, 2009.
http://www3.niaid.nih.gov/topics/lymeDisease/PDF/LymeDisease.pdf
U.S. Food and Drug Administration. Beware of Ticks …& Lyme Disease. Accessed March 10, 2009.
http://www.fda.gov/consumer/updates/lymedisease062707.html
